centroid of contour/object in opencv in c?

Question

is there some good and better way to find centroid of contour in opencv, without using built in functions?

Answer 1

While Sonaten's answer is perfectly correct, there is a simple way to do it: Use the dedicated opencv function for that: moments()

http://opencv.itseez.com/modules/imgproc/doc/structural_analysis_and_shape_descriptors.html?highlight=moments#moments

It does not only returns the centroid, but some more statistics about your shape. And you can send it a contour or a raster shape (binary image), whatever best fits your need.

EDIT

example (modified) from "Learning OpenCV", by gary bradsky

CvMoments moments; 
double M00, M01, M10;

cvMoments(contour,&moments); 
M00 = cvGetSpatialMoment(&moments,0,0); 
M10 = cvGetSpatialMoment(&moments,1,0); 
M01 = cvGetSpatialMoment(&moments,0,1); 
centers[i].x = (int)(M10/M00); 
centers[i].y = (int)(M01/M00);